1. Field of Invention
This invention relates to a soldering structure between a tab of a bus bar and a printed substrate. More particularly, in the case where the printed substrate and bus bar are contained in a layered manner in an electrical junction box to be mounted on an automobile vehicle, and where the tab of the bus bar is soldered on an electrical conductive material on the printed substrate so that the tab intersects the electrical conductive material in a vertical direction, the soldered portion can be prevented from causing cracks.
2. Description of Related Art
As electrical components to be mounted on an automobile vehicle increase, a printed substrate constituting an ECU (Electronic Control Unit) together with bus bars are contained in the electrical junction box and they are electrically connected to form high density circuits.
FIG. 4 shows a typical connection between an electrical conductive material on a printed substrate and a bus bar in a casing of an electrical junction box. A printed substrate 3 is located in a layered manner above or below a bus bar 2 secured on an insulation plate 1 in a horizontal direction. A tab 2b is formed by bending a body 2a of the bus bar 2 in a vertical direction. The tab 2b enters a tab through-hole 5 formed in an electrical conductive material 4 and the printed substrate 3. A solder 6 electrically interconnects the tab 2b and the electrical conductive material 4 around the tab through-hole 5. See Japanese Patent Public Disclosure 2000-22353.
When the solder 6 interconnects the tab 2b and electrical conductive material 4, the tab 2b made of a brass plate is different from the solder 6 with respect to coefficients of extension at a high temperature. The printed substrate 3 on which the solder 6 interconnects the tab 2b and electrical conductive material 4 is secured to a casing of the electrical junction box by using screws. When the tab 2b extends at a high temperature, a stress is caused in an axial direction in the soldered portion. If this stress increases, the soldered portion between the tab 2b and the electrical conductive material 4 tends to cause cracks.
In order to overcome the above problem, in many cases, a connector connected to the electrical conductive material is attached to the printed substrate and the tab of the bus bar is mated with a female terminal in the connector. See Japanese Patent Public Disclosure HEI 10-1890855 (1998).
However, this connecting means using the connector will increase the number of components and working steps and will further bring the ECU and printed substrate into a large size.
In view of the above problems, an object of the invention is to provide a soldering structure between a tab of a bus bar and a printed substrate that causes no crack.